In measuring prothrombin time, use is made, for example, of a reagent for prothrombin time measurement that contains a tissue factor-containing liposome in which a recombinant tissue factor is associated with a liposome composed of phosphatidylcholine and phosphatidylserine (see, for example, WO 98/48283).
On the other hand, it has recently been proposed, from the viewpoint of the standardization of coagulation tests, that an appropriate range of clotting times and an appropriate international sensitivity index should be determined for reagents for prothrombin time measurement that are used for the assessment of prothrombin time.
However, when conventional reagents for prothrombin time measurement are used to determine the clotting time of normal plasma, there is a desire that these reagents result in measurements that meet both a clotting time within an appropriate range and an appropriate international sensitivity index.
The present invention provides a new reagent for prothrombin time measurement that can ensure measurements that are within an appropriate range of clotting times and have an appropriate international sensitivity index when the coagulation of normal plasma is measured, and a method for production thereof.